Current Status of Synthetic Mammalian Embryo Models.

Advances in three-dimensional culture technologies have facilitated the development of synthetic embryo models, such as blastoids, through the co-culturing of diverse stem cell types. These in vitro models enable precise investigation of developmental processes, including gastrulation, neurulation, and lineage specification, thereby advancing our understanding of early embryogenesis. By providing controllable, ethically viable platforms, they help circumvent the limitations of in vivo mammalian embryo studies and contribute to developing regenerative medicine strategies. Nonetheless, ethical challenges, particularly regarding human applications, persist. Comparative studies across various species-such as mice, humans, non-human primates, and ungulates, like pigs and cattle-offer crucial insights into both species-specific and conserved developmental mechanisms. In this review, we outline the species-specific differences in embryonic development and discuss recent advancements in stem cell and synthetic embryo models. Specifically, we focus on the latest stem cell research involving ungulates, such as pigs and cattle, and provide a comprehensive overview of the improvements in synthetic embryo technology. These insights contribute to our understanding of species-specific developmental biology, help improve model efficiency, and guide the development of new models.